KR100305096B1 - Steel cords for reinforcing rubber products and radial tires for air injection using them - Google Patents

Abstract

The steam cord for reinforcing a rubber product of the present invention comprises a core consisting of three steel filaments and a filament having nine corrugated filaments twisted around the core and filaments of 15 corrugated filaments, (H ₂ ) of the waveform formed on the filament with respect to an ideal diameter (D ₁ ) of the _first sheath, the _second sheath being formed by twisting the first sheath in a direction opposite to the twisting direction of the first sheath Of each filament in the second sole defined by the ratio of the formation ratio (F ₁ ) of each filament in the first sole to the amplitude (H ₂ ) of the waveform in the filament with respect to the ideal diameter (D ₂ ) Forming ratio (F ₂ ) are in the range of 0.75-0.95 and F ₁ < F ₂ , respectively. Also, there is provided an air radial tire comprising the above steel cord as a carcass ply.

Description

Steel cords for reinforcing rubber products and radial tires for air injection using them

FIG. 1 is a schematic cross-sectional view of a steel cord having a 3 + 9 + 15 layer (layer) twist structure according to the present invention. FIG.

Fig. 2 is a schematic diagram showing the amplitude of the steel filaments of the waveform. Fig.

Figure 3 is a sectional view of an embodiment of an air-injected radial tire according to the present invention;

FIG. 4 is a schematic view showing the depth of abrasion of steel filaments. FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

1: core 2: first sheath

3: second rest 4: carcass

5: belt layer 6: tread portion

7: Bead core

The present invention relates to an air-injected radial tire using the steel cord as a carcass ply for enhancing tire durability and tire cord for reinforcing air-injected tires, industrial belts and similar rubber products.

As a typical example of a steel cord reinforced rubber product, there are known air injection tires. Among these tires, tires used in trucks, buses and light trucks typically have a carcass ply made of steel cords having a two or three layer twist structure or so-called multilayer twisting structure.

Generally, bending deformation occurs in the steel cord, which is the reinforcing material, while the tire is running. As a result, abrasion occurs in each filament constituting the steel cord, thereby inevitably reducing the cross-sectional area of the filament and lowering the rigidity of the steel cord.

If the reduction of the cross-sectional area in a part of the filament constituting the steel cord is severe, such a filament is broken and is liable to impact on tensile or repetitive bending. Once the filament is broken, the tensile stress in the remaining filament is increased to promote the fatigue breakage of the steel cord.

Therefore, in order to improve the durability of the steel cord, it is effective to avoid premature breakage in a part of the filament, and it is also desirable to make the degradation of the rigidity of all the filaments constituting the steel cord equal.

It is therefore an object of the present invention to provide a durable material for a reinforcing steel cord of a rubber product which is capable of uniformly and gently advancing a reduction in cross-sectional area in the filaments constituting the cord, .

The present inventors have found that with respect to steel cords of multilayer twisted construction used in heavy duty air inflated tires, and especially when such steel cords are used in carcass ply of tires, the 3 + 9 + We have done various studies about steel code of 15 + 1 structure. As a result, it has been found that the decrease in stiffness in the filament constituting the outermost layer of the cord is very large, and the main factor for reducing the stiffness is required to ensure the connection of the outermost filaments and the filaments in this type of cord, And wear between the wrap filaments spirally wrapping the outer periphery of the cord.

The inventors have further studied the steel cord with the wrap filament removed to prevent abrasion, the wear due to the rep filament is removed naturally and the decrease in rigidity of the filament in the outermost layer can be suppressed, The connection of the filaments in the cord is deteriorated due to the absence of the filaments and the filaments are separated when the cord is bent excessively so that breakage in a part of the filament due to an abnormal input Which is a factor that significantly degrades the service life of the code. Therefore, in a cord having no wrap filament, it is necessary to ensure the binding of the filaments constituting the cord in order to prevent the deterioration of the effective service life due to the extreme bending input.

If it does not depend on the bond through the wrap filaments, distortion or twisting in the treats used in the carcass ply of the tire, which significantly interferes with the assembly workability of the green tire, is caused.

That is, treats formed by coating a plurality of steel cords arranged in parallel with each other with rubber are cut to a predetermined length and are joined to each other to form a carcass ply or belt layer. However, when using a steel cord which does not take a connection via the wrap filament, a phenomenon occurs in which the end of the try is twisted upward or downward, or only the edge of the cut end is twisted.

As a result, movement of the treat is hampered by distortion or twisting, or it becomes impossible to bond the treats together, so that the accuracy of assembly of the green tire is lowered and workability is lowered. Therefore, even in the cord having no wrap filament, it is required to bind the filament constituting the cord.

That is, the present invention is based on the above knowledge.

According to the present invention, there is provided a staple fiber comprising: a core made of three steel filaments; a first stiff formed by twisting nine filaments around the core; and a steel filament having fifteen corrugated filaments twisting around the first stiff, (F ₁ ) of each filament in a first sheath, which is defined by the ratio of the amplitude (H ₂ ) of the filament's waveform to the ideal diameter (D ₁ ) of the first sheath, and, first and in the second ideal diameter (D ₂₎ forming a non-(F ₂₎ the range of each of each 0.75 ~ 0.95 of each filament in the second polished is defined as the ratio of the amplitude (H ₂₎ of the waveform of the filaments on the polished , And F ₁ < F ₂ are satisfied.

In the steel cord having the above structure, each filament constituting the cord naturally has a constant twisting angle, so that the cross-sectional shape of the cord in the vertical direction of the cord becomes an ellipse close to the circle.

When this shape is viewed as a circle, the ideal diameter of each seed is calculated according to the following equations.

D ₁ = (2? 3/3 + 1) xr _c + 2xr ₁

D ₂ = ( ₂ ? 3/3 + 1) xr _c + 2xr ₁ + 2xr ₂

Where r _c : diameter of filament in core (mm)

r ₁ : Diameter (mm) of the filament in the first shute

r ₂ : Diameter (mm) of the filament in the second shute

In addition, the present invention is characterized in that it comprises a carcass of at least one or more carcass ply extending annularly between a pair of bead portions, wherein the carcass ply is made of an air injection radial Provide tires.

BRIEF DESCRIPTION OF THE DRAWINGS Fig.

1 is a sectional view of a steel cord for reinforcing a rubber product according to the present invention. The three steel filaments hatched in FIG. 1 form the core 1 as the central basic structure of the cord, and nine steel filaments are aligned adjacent to each other and coaxially twisted around the core 1 to form a first sheath 2, and 15 steel filaments are twisted in the direction opposite to the twisting direction of the first sheath 2 around the first sheath to form the second sheath 3.

Each of the filaments constituting the first and second sheets has a waveform as shown in FIG. 2, so that the workability in forming the second sheet 3 around the first sheet 2 is improved , And the binding of the filaments in the cord is certain after kinking.

In forming the filaments for the first and second sheaths 2 and 3, each filament in the first sheath, defined as the ratio of the amplitude (H ₁ ) of the filament's waveform to the ideal diameter D ₁ of the first sheath, the formation ratio (F ₁₎ and a second polished ideal diameter (D ₂₎ forming a non-(F ₂₎ of each filament in the second polished is defined as the ratio of the amplitude (H ₂₎ of the waveform of the filaments of each individual Is in the range of 0.75 to 0.95, and it is necessary to satisfy F ₁ < F ₂ .

Further, the steel cord according to the present invention can be applied, for example, to the carcass 4 in the air-injected radial tire as shown in FIG. 3, reference numeral 5 denotes a belt layer covering the crown portion of the carcass 4 and reference numeral 6 denotes a tread protrusion superposed around the belt layer 5 , And reference numeral 7 denotes a bead core.

As mentioned above, the lowering of the stiffness of the filament in the steel cord with a layer-twisted structure, in particular the lowering of the filament stiffness in the outermost layer, occurs between the filament in the outermost layer and the filament in the outermost layer, It is caused by wear. This is because the contact area between the lap filament and the filament of the outermost layer is small and the contact pressure per unit area is large, causing wear.

In the case of rotating the tire, twisting occurs in the cords of the carousel of the grounded portion of the tire. When such twisting occurs in a direction opposite to the twist direction of the outermost layer, if the woven filaments are wound in a direction opposite to the twisting direction of the filaments constituting the outermost layer, the twist direction of the filaments in the outermost layer The filaments of the wrap filaments and the filaments of the outermost layer move in opposite directions to each other. Because of the large contact pressure per unit area, the reduction of the cross-sectional area in the filaments of the outermost layer due to abrasion with the wraps filaments is promoted by motion in the opposite direction, which inevitably causes a decrease in filament rigidity.

To this end, when the wrap filaments are removed from the cord of the layer-twisted structure, the deterioration of the filament rigidity in the outermost layer can be avoided. However, when the direction of each sheath twist in the cord is the same, as described above, if a large bending input is applied, the filaments of these sheaths are separated and as a result, some of these filaments are broken due to abnormal input, The effective lifetime of the battery can not be improved.

On the contrary, when the wrap filament is removed and a steel cord having a 3 + 9 + 15 layer twisted structure is formed, if the twist direction of the first sheath is opposite to the twist direction of the second sheath, Binds the filaments of the first staple and exerts the binding effect as in the wrap filament.

Further, as compared with the wrap filaments supporting the binding, the number of filaments in the second and fourth filaments supporting the binding is increased and the twisting interval becomes longer, so that the contact pressure between the filaments of the second filament becomes lower, The deterioration of the filament rigidity due to the unevenness becomes negligible.

Furthermore, when the direction of the twisting applied to the filaments of the second sheet is in the same direction as the twisting direction of these filaments, no problem occurs naturally. On the other hand, when the twist is applied in the opposite direction to the twist direction of the second sheath, twisting in the opposite direction to the twist direction of the second sheath in the first sheath is caused to control the separation of the first sheath, Lt; / RTI >

As a result, the first and second sheaths impart a binding force to each other, thereby maintaining the connection between the filaments of each sheath of the cord.

According to the present invention, the forming ratio (F ₁ ) of each filament in the first sheath and the forming ratio (F ₂ ) of each filament in the second sheath are in the range of 0.75 to 0.95, preferably 0.85 to 0.95, and F ₁ ≪ F ₂ , the bond between the filaments in the cord becomes more certain and firmer, thereby improving the stability of the cord itself or the torsion or separation resistance.

In addition, it is effective to improve the workability in the factory by appropriately binding in the code. This is because, as mentioned above, when the tightening in the cord is not sufficient, the cord tends to cause twisting, so that when the cord is coated with rubber, warping or twisting occurs in the formed cord, to be.

Also, as proposed in Japanese Patent Application Laid-Open No. 5-179584, the so-called rubber penetration structure cords in which the rubber penetrates into the gaps between the filaments in the outermost sheet layer, Tend to extend because the bond through the rubber has been applied to the outermost layer of the outermost layer. However, as compared with a cord with a tightly twisted structure, the presence of a gap between the filaments in the seed to form a rubber infiltration structure increases the degree of abrasion, which is not preferable from the viewpoint of cord durability, The resistance to corrosion fatigue is reduced.

Moreover, the effect of sticking to each other by changing the twist direction of the second and the first sheath can be observed in a cord twisted into two layers. In the latter case, the difference in the number of filaments between the core and the shade is increased, so that the force capable of controlling the separation of the stee is reduced and the effect is reduced.

In order to prevent breakage of the filaments in the cord, it is more desirable to reduce the surface strain. Generally, the surface strain of the filament is about (?) = D / 2R where D is the diameter of the filament and R is the radius of curvature when the cord is bent. Therefore, in order to reduce the surface strain? Under a specific bending input R, it is desirable to make the filament diameter D as small as possible.

That is, in the code showing the effect according to the present invention, it is preferable that the filament diameter is less than 0.220 mm in order to prevent breakage of the filament against extreme bending input applied to the carcass ply of the heavy duty air injection radial tire. On the other hand, the lower limit of the filament diameter is preferably 0.150 mm from the viewpoint of productivity and production cost. It is also desirable to use a so-called high-strength steel material having a tensile strength of at least 330 kgf / mm ² per unit area in order to make the filament diameter as small as possible and to ensure the required cord stiffness.

The following examples are given as examples of the present invention and are not intended to limit the present invention thereto.

Air-injected radial tires for trucks and buses with a size of 1000 R 20 16 PR as shown in FIG. 3 are shown in Tables 1 and 2 on a carousel of 22.0 cord / 5 cm end count tires And each steel cord as shown in FIG.

The retention of cord stiffness, filament breakage rate, depth of wear, and workability at the factory were measured for the tire, and the results shown in Tables 1 and 2 were obtained.

The retention of cord stiffness is evaluated as follows: That is, a test tire having air injected under an internal pressure of 8 kgf / cm 2 is subjected to a distance of 300,000 Km or more at a speed of 60 Km / h under a load of 100% And after that, a sample of rubber treated steel cord was taken out of the test tire carousel ply after running and placed in an Instron tensile testing machine and the tensile strength of the sample strength were measured. The retentivity (%) of the cord stiffness is calculated as the ratio of the measured value to the tensile strength value of the cord before assembly of the tire. The calculated value was expressed as an index on the basis of the result value of Comparative Example 1 as 100. [ The larger the value of the index, the greater the maintainability of the code stiffness.

The filament breakage rate was calculated by dividing the number of broken filaments in 10 cords taken out of the carcass ply after running the test tire over a distance of 10.000 Km or more under an internal pressure of 1 kgf / As shown in Fig. The smaller the value of the numerical value is, the better the resistance against filament breakage becomes. Particularly, it is desirable that the filament breakage rate does not exceed 10%.

The depth of wear was measured as follows. The test tires are run on a drum at a travel distance of 100,000 Km or more under the same conditions as those for measuring the maintainability of the cord stiffness and then the steel filaments of each of the first and second treads are taken out of the steel cord in the carousel ply of the tire, As shown in FIG. 4, the amount of filament diameter (D _f ) decreased due to abrasion was measured by each filament in the region of 13 cm 2 cm from the center of the butterfly of the tread.

The maximum value among the measurements is evaluated as the depth of wear. The smaller the value of the numerical value is, the more the resistance against wear is further improved. It is preferable that the depth of wear is not more than 20 占 퐉.

In the workability at the factory, the productivity and the defect rate of the treat including the steel cord at each manufacturing stage from the twist stage to the tire assembly stage were evaluated in three stages. (△) indicates that there is a partial problem (for example, it is required to remove the catch of the movement try), and the indication (×) indicates that there is a big problem The work is delayed due to the holding of the treat in the tire manufacturing machine or the connection between the treats is poor and the assembly accuracy of the green tire is lowered).

[Table 1]

[Table 2]

As can be seen from Tables 1 and 2, Comparative Examples 1, 4, and 6 have good workability in the factory due to binding through lab filaments, but have a large depth of wear.

In Comparative Examples 2 and 5, the depth of abrasion was small, but the workability in the factory was poor. In Comparative Example 3, although the direction of twisting of the core and the sheath was opposite, the effect was reduced.

In Comparative Examples 7 and 8, the forming ratio of the filament in the sheath was out of the range specified in the present invention, and as a result, the workability in the factory was poor.

As described above, in the steel cord according to the present invention, the abrasion between the filament and the wrap filament in the outermost layer of the outermost layer is removed, and the stiffness degradation of the filament in the cord progresses uniformly and gradually, thereby improving the effective life of the cord . As a result, the durability of the rubber product reinforced with such a steel cord, for example, the durability of the air-injected tire, can be improved.

Claims (4)

A steel cord for reinforcing a rubber product, comprising: a core made up of three steel filaments; a first sheath formed by twisting nine filamentary filaments around the core; and a filament having fifteen corrugated filaments, Defined by the ratio of the amplitude (H ₁ ) of the waveform of the filament to the ideal diameter (D ₁ ) of the _first sheath, the second sheath being twisted in a direction opposite to the twisting direction of the first sheath The formation of each filament in the second sole, which is defined as the ratio of the formation ratio (F ₁ ) of each filament in the first sole to the amplitude (H ₂ ) of the formed waveform of the filament to the ideal diameter (D ₂ ) And the ratio (F ₂ ) is in the range of 0.75 to 0.95, respectively, and F ₁ < F ₂ is satisfied. The filament according to claim 1, characterized in that the forming ratio (F ₁ ) of each filament in the first sheath and the forming ratio (F ₂ ) of each filament in the second sheath are in the range of 0.85 to 0.95 A still code. The steel cord according to claim 1, wherein each steel filament has a diameter of 0.150 mm or more and less than 0.220 mm and a tensile strength of 330 kgf / mm ² or more. Characterized in that it comprises a carcass of at least one carcass ply extending between a pair of bead portions, said carcass comprising a steel cord according to any one of claims 1 to 3 Air radial tires.